McCartney explored the complex story of the National Security Agency’s extensive surveillance in her latest project. “The program is complicated and not much is known yet, so we decided to show you what we do know with the help of visuals,” she wrote on Visual.ly’s blog.

The administration, lawmakers and the intelligence community have claimed the National Security Agency (NSA) programs that use data from private companies to track millions of American are legal. One mysterious court has been tasked with determining whether these programs cross the line, but their decisions are secret, and made without public debate.

The surveillance program that first made news involved collecting the metadata on millions of telephone calls with help from telecommunications giant Verizon. The program is complicated and not much is known yet, so we decided to show you what we do know with the help of visuals.

We start with a flow chart about how the NSA-Verizon program works and the players involved, and move on to a graphic that breaks down the Foreign Intelligence Surveillance Court (FISC) and the elusive judges assigned to oversee each FISA application. At its peak in 2007, the FISC approved nearly 2,500 applications, but only denied four.

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